Previously, outboard marine engines have often utilized various means for accomplishing easier starting. For example, such engines may engage a "warm-up" lever which manually advances the ignition timing and partially opens the carburetor throttle plate. The function of such arrangement is to increase the idle speed and the air/fuel ratio of the engine when it is started. These conditions allow the engine to start easier and run more smoothly until it has warmed up to its standard operating temperature.
While many other engine ignition systems have utilized various means to selectively advance the ignition timing characteristic during operation, none of these systems has been adapted to selectively change the engine timing characteristic as a function of the temperature of the engine during its warm-up phase, as well as during a predetermined time period regardless of the temperature of the engine, and as a function of the operating speed of the engine, particularly when operated at a relatively high speed.
A multi-variable ignition system for outboard marine engines or the like, which selectively adapts ignition scheduling on this basis is illustrated in U.S. Pat. No. 4,858,585, entitled, "Electronically Assisted Engine Starting Means" by Gregry M. Remmers, which was filed on Dec. 11, 1987, and which is assigned to the assignee of the present invention.
The system of Remmers '585 provides an improved ignition system which utilizes a signal proportional to the speed of the engine and couples such speed signal with other signals representing additional engine operating conditions to selectively modify the ignition timing characteristic of the engine to accomplish the functional operational characteristics of: (1) providing protection against engine damage that may be caused by a runaway speed condition; (2) providing a desirable ignition advance during the warm-up period of the engine; (3) providing a desirable ignition advance during the initial engine start up period, irrespective of the temperature of the engine (i.e., even when the engine is warm as a result of having been previously operated); and (4) providing protection against damage that may be caused by advancing the timing characteristic while operating the engine above a predetermined operating speed.
A dual schedule ignition system including the advantages of Remmers U.S. Pat. No. 4,858,585 and disclosing, inter alia, a novel and improved time base generator and distributor system is illustrated in U.S. Continuation-in-part patent application Ser. No. 315,147, entitled "Dual Schedule Ignition System" by Gregry M. Remmers, which was filed on Feb. 24, 1989 and which is assigned to the same assignee as the present invention.
The disclosures of Remmers (U.S. Pat. No. 4,858,585) and Remmers (Ser. No. 315,147) are hereby expressly incorporated by reference herein.
The time base generator of Remmers (Ser. No. 315,147) is implemented opto-electronically by having an encoder disk with timing features rotated synchronously with the engine crankshaft past an illumination source which is optically coupled to a photo-sensitive element. The timing features are positioned on the disk such that each feature is a predetermined number of degrees of engine rotation in duration. A digital waveform is generated indicating the presence or absence of a particular feature and two pulse trains are derived from each pulse of the waveform, where the first is indicative of the leading edge of the feature and the second is indicative of the trailing edge of the feature.
When the encoder disk is rotated in synchronism with the engine crankshaft, the two trains of pulses form a time base where one pulse train is advanced over the second pulse train by the duration of each timing feature. The timing of the pulse trains relative to actual crankshaft position is varied by movement of the illumination source and photo-sensitive element relative to the encoder disk and is scheduled based upon various engine operating parameters.
The first train of pulses provides an advanced ignition timing schedule while the second train of pulses provides a non-advanced ignition timing schedule. The electrical pulse generator and distributor receives the two pulse trains and selects between the two based upon receiving an advance signal or a non-advanced signal. Alternatively, both schedules are inhibited by an inhibit signal. The selected pulse schedule is distributed to the correct cylinders in the firing sequence of the engine to ignite the engine.
A control circuit generates the advance, non-advanced, and inhibit signals based upon time, engine temperature, and starting condition. Preferably, the advance signal is generated during the starting of the engine and for a short predetermined period thereafter. If the engine is not then operating above a warm up temperature, the advance signal is continued until this condition occurs. Regardless of the warm-up status and time of running, if the engine is being operated in excess of a first engine speed, the non-advanced signal is generated. In addition, if a third engine speed is exceeded, the inhibit signal is generated disabling ignition pulses from both schedules. The inhibit signal is also generated if the engine exceeds a second speed and an overheated engine temperature exists. The first speed is, in general, lower than the second speed, which is lower than the third speed. The overheat temperature is, in general, higher than the warm-up temperature.
While this dual schedule ignition system and other capacitive discharge ignition systems provide a number of advantages, it is possible with such electronic ignition systems for the engine to operate in the reverse direction. By reverse engine operation what is meant is rotation of the engine oppositely to its preferred normal rotation direction, i.e., counterclockwise instead of clockwise for most engines including outboard marine engines. This operation can be detrimental to engine life, durability, and performance because most engines are only timed and designed for forward operation. The water pumps of many engines only operate in the forward direction which could lead to rapid engine damage. Moreover, the gear patterns for the transmissions, gear boxes, propellers, etc. will be reversed which could cause a water craft to back-up when in forward, and could also be detrimental to the mechanical elements of the drive train.
Thus, while the referenced dual ignition schedule system of Remmers is advantageous in timing the engine operation, it would also be of advantage to prevent reverse engine operation with such system.
There have in the past been ignition systems which include means for preventing reverse engine operation. U.S. Pat. No. 3,795,235 by Donohue, et al. comprises a trigger coil which is energized periodically to produce a pulse which times the ignition system for spark generation. A metallic shoe is added in the reverse direction to cause a premature spark so far in advance of the top dead center position of a piston so as to preclude continued engine rotation in the undesired direction.
Also, U.S. Pat. No. 4,276,868 by Burrows, et al. has a charge coil arrangement which produces a charging pulse to the ignition system and a separate trigger pulse. The production of the charging pulse occurs so far in advance of engine top dead center during forward operation that the corresponding pulse occurring during reverse engine rotation is so far after top dead center as to prevent reverse engine operation.
Another ignition system of this type is disclosed in U.S. Pat. No. 4,074,699 by Cavil.
Another ignition system having a magnetic pick-up sensor and a trigger wheel for timing trigger pulses in a capacitive discharge system is disclosed in the Johnson Outboard Motor Service Manual (1969) at FIGS. 4-1, 4-2, and 4-3. An anti-reverse running switch is mechanically activated during reverse engine operation to ground the pick-up sensor.
These systems for preventing reverse engine operation are mostly mechanical or electro-mechanical and relatively incompatible with the opto-electronic type of trigger system of Remmers (Ser. No. 315,147).